This invention relates to a liquid phase process for the selective homogeneous catalytic hydrodechlorination of a chlorofluorocarbon compound by reacting the compound with hydrogen while in solution with a Periodic Table Group 8-10 metal complex catalyst which contains tertiary Periodic Table Group 15 ligands without added base.
By Periodic Table Group, Applicant includes those elements organized in Groups described as the "new notation" in the Periodic Table appearing in the CRC Handbook of Chemistry and Physics, 67th Edition, CRC Press (1986-1987).
Chlorofluorocarbons are considered to be detrimental toward the Earth's ozone layer. There is a world-wide effort to develop processes that will replace one or more of the chlorine atom(s) in certain chlorofluorocarbons with hydrogen. For example, 1,1,1,2-tetrafluoroethane (HFC-134a), a hydrofluorocarbon is being considered as a replacement for dichlorodifluoromethane (CFC-12) in refrigeration systems because of its refrigerant properties and zero ozone depletion potential.
There is thus a need for manufacturing processes that provide fluorocarbons that contain less or ideally no chlorine.
One method of reducing the chlorine content of halogen-substituted hydrocarbons containing chlorine as well as fluorine is reacting such organic starting materials with hydrogen in the presence of a hydrogenation catalyst (e.g., supported Periodic Table Groups 7-10 metal catalysts). British Patent Specification 1,578,933 discloses, for example, that HFC-134a can be prepared by the hydrogenolysis of 2,2-dichloro-1,1,1,2-tetrafluoroethane (CFC-114a) or 1,1,1,2-tetrafluorochloroethane (HCFC-124) over palladium on carbon or palladium on alumina hydrogenation catalysts. These processes are typically run in the gas or liquid phase with a solid heterogeneous catalyst.
The prior art (Lokteva et al., Izv. Akad. Nauk. SSSR, Ser. Khim., 1989, (3), 539-42; Ferrughelli and Horvath, J. C. S., Chem. Commun., 1992, 806) teaches hydrodechlorination using soluble homogeneous catalysts which require an excess of added base (NaOH, NEt.sub.3) for removal of the HCl product. The present invention requires no added base.